Tracking a stuck letter

I sent a letter RB004198942PK to Austria last month. I do not know why the post office portal shows the destination country as "Netherlands". It reached Neth on 28th Apr. And no movement been shown after it.
I asked the person i sent to ask his post office but no movement have been shown from hinm since then.
Can anybody from Austria or Netherlands help me somehow.

It is the second case with me. Just recently i sent a letter RB000973400PK to colombia, My post office portal showed it for USA. The letter reached USA and came back for "Address" not being reachable.

Hi,
the letter to Austria arrived in Austria.
It seems that some took it out of a PO Box on 6th of May:

The other letter I can´t track.
Sorry

It is not fair. I have asked a number of times if it reached or not but i did not get a reply.

A few months ago, I posted some coins to Italy. When checking the tracking of the package, I noticed that it was being transported to Indonesia. This baffled me for some time. Later, the tracking system stated that it was indeed on its way to Italy. It arrived in the correct city, but then stated that it was being returned to sender.
I received a letter from the Post Office, also stating that it was being returned to me, but could take 12 weeks.
As of today, it has not been delivered to me.

Thank you very much for the feed back. I got a reply too, The letter has been recieved in Austria.